Here you go, I believe its called the "4 rings of death" It is common, so you are not alone. Here is an article exactly on it, the cause, symptoms, and "things to try to fix it" I hope you get it worked out: http://support.microsoft.com/kb/906652?sd=xbox PS: I also heard a moist towel works but do not try that unless you research. Hope you get it to work!
Three lights is the common one. I'm not sure about four. They've extended the warranty recently so if you go to xbox.com and register the system you should be able to send it for repairs or replacement.